Packaging system for modular power cells

ABSTRACT

A power delivery system includes a group of removable power cells. Each power cell includes a water cooled heat sink, an air intake, and an air output. The system also includes a heat exchanger. The heat exchanger draws air from the cells, cools it, and recirculates the cooled air to the cells via each cell&#39;s air intake. The cell may be designed so that components that are not near the heat sink are cooled by air from the intake before that air reaches the heat sink.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application claims priority to, and incorporates byreference in its entirety, pending U.S. Provisional Patent ApplicationNo. 60/713,197, entitled “Packaging method for modular multilevel powercells and system infrastructure,” filed Aug. 31, 2005.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH

Not applicable.

NAMES OF PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

INCORPORATION BY REFERENCE OF MATERIAL ON DISK

Not applicable.

BACKGROUND

1. Technical Field

This application relates generally to the field of power deliverysystems.

2. Description of the Related Art

In recent years, circuits for medium-voltage variable frequency drive(VFD) applications have received attention. Several novel methods havebeen introduced in the past decade. For example, in a circuit comprisingseries-connected inverters as described in U.S. Pat. No. 5,625,545 toHammond, the disclosure of which is incorporated herein by reference inits entirety, an inverter or power cell 110 includes a three-phasediode-bridge rectifier 112, one or more direct current (DC) capacitors114, and an H-bridge inverter 116. The rectifier 112 converts the input118 alternating current (AC) voltage to a substantially constant DCvoltage that is supported by the capacitors 114 that are connectedacross the rectifier 112 output. The output stage of the inverter 110includes an H-bridge inverter 116 that includes two poles, a left poleand a right pole, each with two devices. The inverter 110 transforms theDC voltage across the DC capacitors 114 to an AC output 120 usingpulse-width modulation (PWM) of the semiconductor devices in theH-bridge inverter 116.

Other circuits and drives for medium voltage and high voltage motorcontrol are available. In general medium voltage refers to a ratedvoltage greater than 690 volts (V) and less than 69 kilovolts (kV). Insome embodiments, medium voltage may be a voltage between about 1000 Vand about 69 kV. High voltage ratings exceed such medium voltageratings. In many such systems, modular power cells are used. Industryoften seeks ways to reduce the size of such systems, increase the lifeand reliability of the systems, and permit the systems to keep operatingunder on or more fault conditions.

The disclosure contained herein describes attempts to solve one or moreof the problems described above.

SUMMARY

In an embodiment, a power delivery system includes a plurality ofremovable power cells positioned within a housing structure. Each powercell includes a water cooled heat sink, an air intake, and an airoutput. The system also includes a heat exchanger. Each cell may bepositioned to receive air into the air intake and expel the air into anair plenum. The heat exchanger may be positioned to receive the air fromthe air plenum, cool the air, and recirculate the cooled air to thecells via each cell's air intake. During operation, the air that isexpelled into the air plenum by a cell may be warmer than the air thatis received into the air intake of the cell. In addition, each cell'sheat sink may be connected to a water intake and a water output, andduring operation, the water that is expelled through the water output bya cell may be warmer than the water that is received into the waterintake of the same cell. In some embodiments, each power cell includes aplurality of capacitor connectors and a plurality of transistors. Thecapacitor connectors may be positioned closer to the air intake whencompared to the position of the heat sink, and the heat sink may bepositioned closer to the air outlet when compared to the position of thecapacitor connectors. During operation, most air circulating through thecell may contact the capacitor connectors before contacting the heatsink. Each power cell also may include a circuit board that ispositioned closer to the air intake when compared to the position of theheat sink. The system also may include a back plane positioned betweenthe cells and the air plenum, a plurality of power delivery bussespositioned within the air plenum to deliver power to the cells, and aplurality of power return busses positioned within the air plenum toreceive power from the cells and deliver the power to a load. The systemalso may include a water delivery manifold and a water return manifold,such that each manifold comprises a plurality of self-sealingconnections, wherein each connection opens when a cell is connected tothe connection and closes when a cell is removed from the connection.

In an alternate embodiment, a power delivery system, includes aplurality of removable power cells positioned within a housingstructure. Each power cell may include an input bus, an output bus, anair intake, and an air output, a water cooled sink that is connected toa water intake and a water output, a water delivery manifold and a waterreturn manifold. Each water manifold may include self-sealingconnections, such that each connection opens when a cell is connected tothe connection and closes when a cell is removed from the connection.The system also may include an air plenum and a heat exchanger thatreceives the air from the air plenum, cools the air, and recirculatesthe cooled air to the cells via each cell's air intake. Each cell may bepositioned to receive air and expel the air into the air plenum, andeach cell also may be positioned to receive water through its waterintake and expel the water from its water output. During operation, theair that is expelled into the air plenum by a cell may be warmer thanthe air that is received into the air intake of the cell, and the waterthat is expelled through the water output by the cell may be warmer thanthe water that is received into the water intake of the cell. In someembodiments, each power cell may include a plurality of capacitorconnectors and a plurality of transistors. The capacitor connectors maybe positioned closer to the air intake when compared to the position ofthe heat sink, and the heat sink may be positioned closer to the airoutlet when compared to the position of the capacitor connectors so thatmost air circulating through the cell may contact the capacitorconnectors before contacting the hear sink. In some embodiments, eachpower cell also may include a circuit board that is positioned closer tothe air intake when compared to the position of the heat sink. Thesystem also may include a back plane positioned between the cells andthe air plenum, a plurality of power delivery busses positioned withinthe air plenum to deliver power to the cells, and a plurality of powerreturn busses positioned within the air plenum to receive power from thecells and deliver the power to a load.

In some embodiments, a power delivery system also may include aplurality of removable power cells positioned within a housingstructure, wherein each power cell comprising an air intake, an airoutput, and a water cooled sink. The system may include a water deliverymanifold and a water return manifold connected to the water cooled sink,wherein each manifold comprises a plurality of self-sealing connections,wherein each connection opens when a cell is connected to the connectionand closes when a cell is removed from the connection. The system alsomay include an air plenum, and a heat exchanger that receives the airfrom the air plenum, cools the air, and recirculates the cooled air tothe cells via each cell's air intake. Each cell may be positioned toreceive air and expel the air into the air plenum, and during operation,the air that is expelled into the air plenum by a cell is warmer thanthe air that is received into the air intake of the cell. Each powercell may include a plurality of capacitor connectors that are positionedcloser to the air intake when compared to the position of the heat sink.The heat sink may be positioned closer to the air outlet when comparedto the position of the capacitor connectors so that during operation,most air circulating through the cell contacts the capacitor connectorsbefore contacting the heat sink. In some embodiments, each power cellalso may include a circuit board that is positioned closer to the airintake when compared to the position of the heat sink. The system alsomay include a back plane positioned between the cells and the airplenum, a plurality of power delivery busses positioned within the airplenum to deliver power to the cells, and a plurality of power returnbusses positioned within the air plenum to receive power from the cellsand deliver the power to a load.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram illustrating exemplary features of a priorart power cell.

FIG. 2 depicts a circuit comprising a plurality of power cells connectedto a load.

FIG. 3A is a rear perspective view and FIG. 3B is a front perspectiveview of an exemplary power cell housing structure, while FIGS. 3C and 3Dillustrate exemplary connecting members for the power cell structure.

FIG. 4 illustrates an exemplary power cell internal structure.

FIG. 5 illustrates an exemplary support structure for multiple powercells.

FIG. 6 illustrates an exemplary power cell system in a housing.

FIG. 7 illustrates an exemplary water delivery system.

DETAILED DESCRIPTION

Before the present methods, systems and materials are described, it isto be understood that this disclosure is not limited to the particularmethodologies, systems and materials described, as these may vary. It isalso to be understood that the terminology used in the description isfor the purpose of describing the particular versions or embodimentsonly, and is not intended to limit the scope. For example, as usedherein and in the appended claims, the singular forms “a,” “an,” and“the” include plural references unless the context clearly dictatesotherwise. In addition, the term “comprising” is intended to mean“including but not limited to.” Unless defined otherwise, all technicaland scientific terms used herein have the same meanings as commonlyunderstood by one of ordinary skill in the art.

In various embodiments, a multi-level power circuit a plurality of powercells to drive a load. FIG. 2 illustrates an exemplary embodiment of acircuit having such power cells. In FIG. 2, a transformer 210 deliversthree-phase, medium-voltage power to a load 230 such as a three-phaseinduction motor via an array of single-phase inverters (also referred toas power cells). The transformer 210 includes primary windings 212 thatexcite a number of secondary windings 214-225. Although primary winding212 is illustrated as having a star configuration, a mesh configurationis also possible. Further, although secondary windings 214-225 areillustrated as having a mesh configuration, star-configured secondarywindings are possible, or a combination of star and mesh windings may beused. Further, the number of secondary windings illustrated in FIG. 2 ismerely exemplary, and other numbers of secondary windings are possible.The circuit may be used for medium voltage applications or, in someembodiments, other applications.

Any number of ranks of power cells are connected between the transformer210 and the load 230. A “rank” is considered to be a three-phase set, ora group of power cells established across each of the three phases ofthe power delivery system. Referring to FIG. 2, rank 250 includes powercells 251-253, rank 260 includes power cells 261-263, rank 270 includespower cells 271-273, and rank 280 includes power cells 281-283. Fewerthan four ranks, or more than four ranks, are possible. A centralcontrol system 295 sends command signals to local controls in each cellover fiber optics or another wired or wireless communications medium290.

The power cells described in FIG. 2 provide a modular, multilevel systemthat allows cells to be replaced as needed to accommodate differentdesign requirements, or to replace a failed cell. FIG. 3A illustrates arear perspective view and FIG. 3B illustrates a front perspective viewof exemplary power cell structure 310. The power cell 310 includes achassis 312 and a plurality of power input/output connectors 325.

Referring to FIG. 3C, power connector 325 for the power cell may includea conducting arm 371 that extends from a mounting block 370. Referringto FIG. 3D, conducting arm 371 may be sized to make a secure electricalconnection with a power connector 380 for the power bus. For example,conducting arm 371 may fit between and contact a pair of conducting arms381, 382 of the power bus connector 380. In some embodiments, power busconnector 380 may include a support 383 that helps to make asubstantially rigid connection. Other power connector configurations arepossible. In addition, in some embodiments a structure similar to powerbus connector 380 may be included with the power cell, while a structuresimilar to 325 may be included with the power bus.

Returning to FIGS. 3A and 3B, the chassis 312 encloses variouscomponents of the electronic module 310, such as one or more capacitors,printed circuit boards, heat sinks, etc. The chassis 312 may befabricated from any suitable material, such as galvanized steel oranother metal, that both mechanically and electromagnetically isolatesthe power cell from other power cells in the system during both normaloperation and many abnormal operating conditions. The chassis 312 mayserve to protect internal components of the electronic module 310 fromdamage during shipping and handling, and it may be configured in amanner such that the electronic module 310 can be placed on any of itssides without causing any damage to the components of the electronicmodule 310. According to various embodiments, the chassis 312 may becomprised of several portions connected together, and one or moreportions of the chassis 312 may be removable. In addition, the chassis312 may be of a thickness sufficient to prevent any debris resultingfrom a failure of the internal components of the electronic module 310from exiting the space enclosed by the chassis 312, thereby preventingany collateral damage to other components in the vicinity of theelectronic module 310. The chassis 312 may also serve to provide a lowimpedance path for arcing faults within the chassis to minimizepotential damage caused thereby.

Exemplary internal components of the cell may include an electronicsassembly that may include current-controlling devices or switches suchas insulated gate bipolar transistor (IGBT) modules, other transistors,thyristors and one or more rectifier modules. The IGBTs may be separatedfor I/O bus locations and to increase thermal performance. The cell mayinclude one or more control boards or other electronic devices that maybe positioned near the front end 311 of the cell, with an optionalaccess opening 315 covered by a door or panel that may be opened orremoved. The interior front area of the cell may include a plurality ofcapacitor connectors 330 that receive capacitors for cell operation. Thecapacitors (not shown) may extend from the capacitor connectors towardthe rear 321 of the cell or in another direction. The lower portion ofthe cell, where the capacitors are positioned, may be covered by ahousing that serves as a lower portion (not shown) of chassis 312.

The cell 312 may contain a water cooling system to remove heat from thecell during operation. The cell's internal water cooling pipes maycontain a water inlet connection 330 and water outlet connection 332 toreceive cool water into the cell and expel water from the cell,respectively, via one or more hoses or conduits.

Referring to FIG. 4, the hose connections may deliver water to andreceive water from input water conduit 410 and output water conduit 412that are connected to deliver fluid to and from a water cooled heat sink416, which is a sealed container that holds cooling water at a positionthat is effective to absorb heat from components of the cell, such as alocation under IGBT devices connected to busses 422, 423 and 424 andother components of the cell. Busses 422, 423 and 424 may beelectrically connected to one or more power plugs 325 (see FIG. 3). Abus may be any electrically conductive delivery device, such as a wire,rigid or flexible piece of metal, conductive polymer, or anothermaterial. Referring to FIG. 3, the heat sink and IGBTs are typicallylocated near the rear 321 of the cell. The water for the heat sink maycool the IGBTs. Deionized water is preferred, and the water may berecirculated to an air-to-water or water-to-water heat exchanger that islocated external to the cell.

In addition to a water cooling structure, referring back to FIG. 3, eachcell may include an air inlet 340 and an air outlet 342 that directs airthrough the cell 310 so that the air flows over components such ascapacitor connections, electronics and control boards, power switches,bus connectors, and/or the busses themselves. Each of the air intake andoutput may be covered by a filter or grill in some embodiments.Preferably, the cell 310 components are positioned so that air flowsfirst over the capacitor connections, and/or circuit boards, with airflow over the heat sink occurring later in the air stream. This occursby positioning capacitor connections 330 and circuit boards (underopening 315) near the front of the cell, while positioning the heat sink416 near the air outlet 342 or rear area 321 of the cell. Thus, the airmay be cooler when it passes across components that are not also nearthe water-cooled heat sink, while air may be warmer in areas where theheat sink also provides cooling capability.

FIG. 5 illustrates an exemplary support structure 544 for multiple powercells, such as nine cells, within a housing wherein each power cell orother electronic module is positioned on one or more mounting rails 546so that the rear of each cell faces a backplane 548 and the cell's powerplugs contact the cell power connections 521-525 within an air plenum.The backplane 548 may be fabricated from any suitable non-conductivematerial, such as a high-strength non-conductive laminate material, andit separates the air plenum from the heat exchange system that removesheat from the individual cells.

FIG. 6 illustrates an exemplary power cell system 600 containing anynumber of replaceable power cells 310 connected to power input/outputbuswork 605 via connecting buswork 620. Back plane 548 separates thepower cells 310 from the air plenum 610. As air moves into the front ofa cell, the air may absorb heat from the components of the cell. The airthat leaves the cell at its rear and passes through an opening in theback plane 548 is typically warmer than the air that entered the cell. Aheat exchanger 640 receives the warm or hot air from the air plenum 610,cools the air and returns cooled air to the front of the cells via anair delivery space 630 that is located within system housing 650. Anysuitable air cooling system may be used as the heat exchanger 640.Preferably, heat exchanger 640 is located on or near the top of thehousing 650, although other locations are possible. Thus, the system maydirect air from the rear of the cells, through the heat exchanger in aconstant, recirculating manner. In the forced air delivery systemdescribed herein, in some embodiments the recirculation of air mayreduce ionization of the air and the arcing faults associated with suchionization.

FIG. 7 illustrates a water delivery system that also may be includedwithin the housing. Each cell 310 has input and output hose connections330 and 332 that are connected to water delivery 740 and return 742manifolds via connecting conduits 710 and 712. Water manifolds andconduits may be made of any material suitable for delivering hot andcold water, such as noncorrosive metal, rubber, silicon, PVC, plastic orany other suitable material. The connections between hose connections330 and 332 and connecting conduits 710 and 712 may be self-sealing sothat an individual power cell cal be removed from the system withoutbreaking the water paths to other cells. Any suitable sealing device,such as a valve that opens upon connection and closes upondisconnection, may be used for this purpose. Water delivery 740 andreturn 742 manifolds may be located within the air plenum 610 of thepower delivery system 600 (referring to FIG. 6). Water, preferablydeionized, may be circulated to or from an external heat exchanger to becooled.

In medium voltage systems, the air entering the cell may be controlledto a temperature of approximately 55° C., while the water delivered tothe cells may be controlled to a temperature of approximately 47° C.Other temperatures are possible. The air and water may absorb heat whileinside the cells, and the air and water exiting the cell may, in someembodiments, be several degrees warmer than the air and water thatenters the cells.

Still other embodiments will become readily apparent to those skilled inthis art from reading the above-recited detailed description anddrawings of certain exemplary embodiments. It should be understood thatnumerous variations, modifications, and additional embodiments arepossible, and accordingly, all such variations, modifications, andembodiments are to be regarded as being within the spirit and scope ofthis application.

1. A power delivery system, comprising: a plurality of removable powercells positioned within a housing structure, each power cell comprisinga water cooled heat sink, an air intake, and an air output; and a heatexchanger; wherein each cell is positioned to receive air into the airintake and expel the air into an air plenum; and wherein the heatexchanger is positioned to receive the air from the air plenum, cool theair, and recirculate the cooled air to the cells via each cell's airintake.
 2. The system of claim 1 wherein, during operation, the air thatis expelled into the air plenum by a cell is warmer than the air that isreceived into the air intake of the cell.
 3. The system of claim 2wherein: each cell's heat sink is connected to a water intake and awater output; and during operation, the water that is expelled throughthe water output by a cell is warmer than the water that is receivedinto the water intake of the same cell.
 4. The system of claim 1 whereineach power cell comprises a plurality of capacitor connectors and aplurality of transistors.
 5. The system of claim 4, wherein thecapacitor connectors are positioned closer to the air intake whencompared to the position of the heat sink, and the heat sink ispositioned closer to the air outlet when compared to the position of thecapacitor connectors.
 6. The system of claim 5, wherein duringoperation, most air circulating through the cell contacts the capacitorconnectors before contacting the heat sink.
 7. The system of claim 5,wherein each power cell further comprises a circuit board that ispositioned closer to the air intake when compared to the position of theheat sink.
 8. The system of claim 1 further comprising: a back planepositioned between the cells and the air plenum; a plurality of powerdelivery busses positioned within the air plenum to deliver power to thecells; and a plurality of power return busses positioned within the airplenum to receive power from the cells and deliver the power to a load.9. The system of claim 1, further comprising a water delivery manifoldand a water return manifold, wherein each manifold comprises a pluralityof self-sealing connections, wherein each connection opens when a cellis connected to the connection and closes when a cell is removed fromthe connection.
 10. A power delivery system, comprising: a plurality ofremovable power cells positioned within a housing structure, each powercell comprising an input bus, an output bus, an air intake, and an airoutput, and a water cooled sink that is connected to a water intake anda water output; a water delivery manifold and a water return manifold,wherein each manifold comprises a plurality of self-sealing connections,wherein each connection opens when a cell is connected to the connectionand closes when a cell is removed from the connection; an air plenum;and a heat exchanger that receives the air from the air plenum, coolsthe air, and recirculates the cooled air to the cells via each cell'sair intake; wherein each cell is positioned to receive air and expel theair into the air plenum, and wherein each cell is further positioned toreceive water through its water intake and expel the water from itswater output.
 11. The system of claim 10 wherein, during operation: theair that is expelled into the air plenum by a cell is warmer than theair that is received into the air intake of the cell; and the water thatis expelled through the water output by the cell is warmer than thewater that is received into the water intake of the cell.
 12. The systemof claim 10 wherein each power cell comprises a plurality of capacitorconnectors and a plurality of transistors.
 13. The system of claim 12,wherein the capacitor connectors are positioned closer to the air intakewhen compared to the position of the heat sink, and the heat sink ispositioned closer to the air outlet when compared to the position of thecapacitor connectors.
 14. The system of claim 12, wherein duringoperation, most air circulating through the cell contacts the capacitorconnectors before contacting the hear sink.
 15. The system of claim 12,wherein each power cell further comprises a circuit board that ispositioned closer to the air intake when compared to the position of theheat sink.
 16. The system of claim 10 further comprising: a back planepositioned between the cells and the air plenum; a plurality of powerdelivery busses positioned within the air plenum to deliver power to thecells; and a plurality of power return busses positioned within the airplenum to receive power from the cells and deliver the power to a load.17. A power delivery system, comprising: a plurality of removable powercells positioned within a housing structure, each power cell comprisingan air intake, an air output, and a water cooled sink; a water deliverymanifold and a water return manifold connected to the water cooled sink,wherein each manifold comprises a plurality of self-sealing connections,wherein each connection opens when a cell is connected to the connectionand closes when a cell is removed from the connection; an air plenum;and a heat exchanger that receives the air from the air plenum, coolsthe air, and recirculates the cooled air to the cells via each cell'sair intake; wherein each cell is positioned to receive air and expel theair into the air plenum, and during operation, the air that is expelledinto the air plenum by a cell is warmer than the air that is receivedinto the air intake of the-cell; wherein each power cell comprises aplurality of capacitor connectors, the capacitor connectors arepositioned closer to the air intake when compared to the position of theheat sink, and the heat sink is positioned closer to the air outlet whencompared to the position of the capacitor connectors.
 18. The system ofclaim 17, wherein during operation, most air circulating through thecell contacts the capacitor connectors before contacting the heat sink.19. The system of claim 17, wherein each power cell further comprises acircuit board that is positioned closer to the air intake when comparedto the position of the heat sink.
 20. The system of claim 17 furthercomprising: a back plane positioned between the cells and the airplenum; a plurality of power delivery busses positioned within the airplenum to deliver power to the cells; and a plurality of power returnbusses positioned within the air plenum to receive power from the cellsand deliver the power to a load.